Portable fluid warmer

ABSTRACT

A warming device, for warming infusion or transfusion fluids by an exothermic reaction of a reactive liquid. The device comprises a reaction chamber and a secondary chamber. The reaction chamber and the secondary chamber are aligned end on and are abutting. The reaction chamber contains a trigger and the secondary chamber contains the reactive liquid.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/014,061 filed on Feb. 3, 2016, which is a divisional of U.S. patentapplication Ser. No. 13/881,737 filed on Apr. 26, 2013, which is anational stage entry of PCT/AU2011/001369 filed Oct. 27, 2011, under theInternational Convention claiming priority over Australian PatentApplication No. 2010904779 filed Oct. 27, 2010.

FIELD OF THE INVENTION

The present invention relates to a compact, self-contained fluid heatingdevice. In particular, the invention relates to devices for heatingfluids such as blood that can be used in remote locations.

BACKGROUND OF THE INVENTION

Blood for transfusions is typically stored at approximately 4° C. Priorto patient transfusions, it is preferable that the blood be warmed to atemperature substantially the same as that of the living body,approximately 37° C. Failure to warm the blood prior to transfusion, mayresult in the patient's core temperature dropping to dangerous levelspotentially resulting in hypothermia.

There currently exists a number of portable blood warming devices usedin hospitals. These are typically large and cumbersome devices that drawpower from a mains supply. In some devices the blood is fed into aspiral tube, which is immersed in a water bath whose temperature ismaintained at a set temperature. Other known devices use a heatedjacket, which is wrapped around a blood bag, and draw power from themains supply.

These types of devices, whilst satisfactory in hospital or clinicalsituations where a constant source of power is available, are notconvenient to use in situations that are remote from reliable powersources or in remote locations where it is not practical to carry suchlarge and cumbersome equipment, such as when a patient is moved betweenwards or geographical locations.

Portable devices for warming blood are also known, such as those devicessold under the THERMAL ANGEL and HOTIV trade marks. Both of theseexisting devices rely on batteries to provide the source for heating theinfusion or transfusion fluid. There are however a number of problemswith batteries including that they are heavy, bulky and requirereplacement or recharging at regular intervals. Given that heatingequipment places substantial load on the batteries, it is not possiblefor these batteries to be small. Additionally, the maintenance issuesassociated with batteries are such that, for example, if the portableblood warmer is used in an emergency vehicle then it is necessary thatregular checks are made on the condition of the battery or indeed thatspare batteries are available such that there is always a source ofpower available. Furthermore, the requirement of batteries in order tooperate the blood warmer dramatically increases the overall weight ofthe apparatus and therefore if rescue workers are required to trek intoa remote location this then places an additional burden on them and maycomplicate matters if the unit fails to operate due to problemsassociated with the power source. The warming devices can also be usedto heat infusion fluids, such as pharmaceuticals and saline fluids.

Portable devices for warming transfusion and infusion fluids usingchemical processes to generate the required heat have also beenattempted. Disclosures of such attempts can be found in patentdocuments, U.S. Pat. Nos. 5,042,455, 4,934,336, WO2003059414,WO2008017456, and by the present inventors' earlier application,WO2006056015.

One potential problem of using chemical reaction described in the priorart to generate the required heat, is the challenge of controlling andregulating the heat generated by the chemical reaction, which otherwisehas the potential to damage the blood or infusion fluids if thetemperature is raised too high. To overcome this problem, the inventorshave experimented with using a chemical reaction that releases latentheat, upon solidification, at approximately 42° C., which is about themaximum temperature blood can tolerate before damage may occur. Resultsof an experiment undertaken by the inventors can be found in thedisclosure, McEwen, M. P. and D. Roxby, “Can latent heat safely warmblood?—in vitro testing of a portable prototype blood warmer.” BMC EmergMed, 2007. 7: p. 8.

The inventors have used crystals that react with a chemical liquid toproduce the reaction that releases the required latent heat. However adifficulty in using these types of chemical reagents in currentlyavailable devices is that the flow of chemical liquid and crystalsthrough the reaction chamber may be too slow. In addition the flow isfurther hampered by the crystallisation of the reagents that may resultin blockages occurring within the reaction chamber. If this occurs thedevice may not be ideal in an emergency situation where the biologicalfluid warmer should preferably be fast acting, otherwise particularly inemergency situations the health of the patient may be compromised.

It is thus desirable to have a device for warming blood, or otherfluids, that is portable, lightweight, disposable, reliable, economicalin cost and manufacture, and that overcomes, or at least substantiallyameliorates, the disadvantages and shortcomings of the prior art, or atleast provides the public with a choice.

It should be appreciated that any discussion of the prior art throughoutthe specification is included solely for the purpose of providing acontext for the present invention and should in no way be considered asan admission that such prior art was widely known or formed part of thecommon general knowledge in the field as it existed before the prioritydate of the application.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, but not necessarily thebroadest aspect, there is proposed a device for warming infusion ortransfusion fluids by an exothermic reaction of a reactive liquid,including at least one reaction chamber containing a trigger, and apassageway extending through said reaction chamber for movement of saidinfusion or transfusion fluids therethrough, wherein the reactive liquidis introduced into said reaction chamber, being at least partiallyevacuated of air, to thereby initiate said exothermic reaction.

The reaction chamber may be held at negative atmospheric pressure oralternatively the reaction chamber may be expandable, whereby whenexpanded the contents of said reaction chamber are at negativeatmospheric pressure, for instance the reaction chamber may becollapsible in a concertina type fashion.

The trigger may be a catalyst or another chemical that reacts with saidreactive liquid resulting in the crystallisation thereof. In one formthe trigger is a chemical trigger, or in another form the trigger is amechanical trigger.

The trigger for initiating the exothermic reaction may be crystals oralternatively the trigger may be a powder or other particulate thatinitiates the exothermic reaction.

The passageway extending through said reaction chamber is isolated fromthe contents of the reaction chamber to inhibit contamination of saidinfusion or transfusion fluids. The passageway extending through thereaction chamber for movement of the infusion or transfusion fluidstherethrough may be a length of flexible tubing.

Preferably the trigger is contained within the reaction chamber and thereactive liquid is contained within a secondary chamber, the reactionand secondary chambers being separated by a frangible or removablebarrier.

The reaction and secondary chambers may be flexible wherein thesecondary chamber may be compressed to rupture the frangible barrier tothereby introduce the reactive liquid into the reaction chamber.

In another form the barrier is a clamp that separates the reaction andsecondary chambers, whereby when the clamp is removed the reactiveliquid is able to flow or be compelled into the reaction chamber.

The inventors have discovered that the reaction can be accelerated byintroducing the reactive liquid into a reaction chamber that is at leastpartially evacuated of air, and that contains a trigger such as crystalsor particulate matter or any other means that induces the reactiveliquid to crystallise. The rapid movement of reactive liquid withrespect to the trigger that initialises or promotes crystallization,enables the growing crystals (solidification) to break and spreadthroughout the reactive liquid without being localized in one part ofthe reaction chamber that may cause blockages.

In addition, it has been found that a liquid chemical can flowrelatively rapidly if there is minimal liquid or gas to displace in thereaction chamber. The rapid flow disrupts, removes or breaks the growingcrystals from localising in one area, which would normally be near theinlet port where the reactive liquid first comes into contact with thetrigger that initiates the crystallization process and would thennormally block or restrict the port. This would then impede or preventall the reactive liquid from entering the chamber, and thus slowing orpreventing a complete chemical reaction from occurring.

The rapid flow of the crystallising liquid chemical can be furtherenhanced by the avoidance of passing the chemical through narrowopenings or large distances. Therefore, in one form the fluid warmer isconstructed such that the average distance for the reactive liquid totravel, from all points in the secondary chamber to all points in thereaction chamber will not exceed half the total length of the fluidpassageway; and openings of larger than 10 square millimetres areprovided for the movement of the chemical within the reaction chamber.

The rapid flow of the crystallising liquid chemical may be yet furtherenhanced by locating the trigger within the reaction chamber away fromboth the inlet port and a main liquid chemical pathway or pathways,through the reaction chamber. Keeping these regions free of the triggercan reduce the tendency for crystals to grow in these regions and blockor impede the movement of the liquid chemical.

Thus, according to one aspect of the current invention, there isprovided a portable, disposable device for warming infusion ortransfusion fluids by an exothermic reaction of a reactive liquid,wherein said device includes; a flexible reaction chamber, being atleast partially evacuated of air, containing a trigger; a passagewayextending through said reaction chamber for movement of said infusion ortransfusion fluids therethrough; a flexible secondary chamber containingsaid reactive liquid, the reaction and secondary chambers beingseparated by a frangible or removable barrier, wherein the reactiveliquid may be introduced into said reaction chamber by rupturing orremoving said barrier to thereby initiate said exothermic reaction; anda compression member for forcing said reactive liquid out of saidsecondary chamber and through said reaction chamber.

Preferably the trigger is held at negative atmospheric pressure withinthe reaction chamber to assist with the flow of the reactive liquidtherethrough.

In one form, when the barrier is removed to start the exothermicreaction, the removal of the barrier causes the reaction and secondarychambers to form one single chamber.

The compression member is used for forcing the reactive liquid into thereaction chamber and past or around the passageway that carries theinfusion or transfusion fluid.

The means for forcing the reactive liquid to move may include the manualmanipulation of the flexible reaction and/or secondary chambers.

In one form the reaction chamber may be formed within a generally planarenvelope constructed from a resiliently flexible material. A portion ofsaid tubing being contained within the envelope, wherein the tubinghaving an inlet and an outlet extending outwardly from within saidenvelope, for passage of a fluid therethrough. The envelope ispreferably atmospherically sealed such that the reaction chamber is atleast partially evacuated of air.

The envelope may be connected to the secondary chamber by way of atleast one port and in one form may be connected by a plurality of ports.

A resiliently flexible bladder may form said secondary chamber whereinthe compression member may extend along a side of said bladder oppositesaid port. The compression member in one form is a generally rigid rod,wherein after removal of the barrier between said reaction and secondarychambers the rod may be progressively folded over the bladder, or thesecondary chamber may be rolled around the rod, to force the reactiveliquid contained therein into the reaction chamber to thereby undergosaid exothermic reaction.

The generally empty bladder may be progressively folded over theflexible envelope or the flexible envelope may be rolled around the rod,to move said reactive liquid throughout the reaction chamber. Thelayering or rolling of the device will reduce the surface area in directcontact with the ambient air and therefore inhibit radiant, convectionand conductive heat loss therefrom. Furthermore, the folding or rollingof the device will inhibit crystals from forming a barrier within thereaction chamber that may inhibit movement of the reactive liquid to theextremities of the reaction chamber.

Alternatively the reaction chamber may be formed within a collapsiblecontainer or box that in one form includes a foldable frame.

The reactive liquid may be any chemical or mixture of chemicals thatproduce an exothermic reaction at the desired temperature and with thedesired amount of heat energy released.

The reactive liquid chemical may be calcium nitrate tetrahydrate. Thetrigger for initiating the exothermic reaction may be calcium nitratetetrahydrate crystals.

The tubing extending through the reaction chamber may be of any suitableconfiguration that maximises the heat transfer from the exothermicreaction to the infusion or transfusion fluid to be warmed within thetubing.

Preferably, the tubing configuration through the reaction chamber isindirect and in one form is a generally planar serpentine arrangement.

Alternatively, the tubing configuration may be in a spring or coiledarrangement, or may be a layered serpentine arrangement.

The trigger for initiating the exothermic reaction in said reactionchamber may be located in close proximity to the barrier between thereaction and secondary chambers.

The reaction chamber may include a means for aiding in the exothermicreaction or transferral of heat. For instance metal strips may becontained within the reaction chamber for conducting heat to said tube.Furthermore crystals, powder or particulate may be positioned throughoutthe reaction chamber to assist in a generally constant reaction throughthe chamber. In one form the crystals, powder or particulate may beattached to the inner wall of reaction chamber, or to the walls of thepassageway adjacent the reaction chamber.

In another aspect of the invention there is proposed a device forwarming infusion or transfusion fluids by an exothermic reaction of areactive liquid, including a reaction chamber containing saidcrystallisation trigger, a secondary chamber containing said reactiveliquid, a passageway for movement of the infusion or transfusion fluidstherethrough extending through both reaction and secondary chambers suchthat the portion of the passageway within the reaction chamber being ina compressed state, and a removable barrier between the two chambers,whereby removal of said barrier causes the crystallisation trigger tocontact the reactive liquid and permits the compressed passageway toexpand, thereby spreading the crystallisation reaction into the reactionchamber.

A further aspect of the invention resides in a method for warminginfusion or transfusion fluids to be administered to a patient, themethod including the steps of: removing a barrier between a reactionchamber and a secondary chamber of a warming device, the reactionchamber, at least partially evacuated of air, containing a trigger, andthe secondary chamber containing a reactive liquid, whereby the removalof the barrier initiates an exothermic reaction of the reactive liquid;and moving said infusion or transfusion fluids through a passagewayintersecting said reaction chamber wherein latent heat released by thereactive liquid warms the fluids passing through said passageway.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate implementations of the inventionand, together with the description and claims, serve to explain theadvantages and principles of the invention. In the drawings:

FIG. 1 is a perspective view of a first embodiment of the portable fluidwarmer of the present invention;

FIG. 2 is side view of the portable fluid warmer of FIG. 1;

FIG. 3 is a perspective view of the portable fluid warmer of FIG. 1 withthe clamp removed;

FIG. 4 is a cross sectional view through AA of the portable fluid warmerof FIG. 3 in the process of being rolled;

FIG. 5 is a perspective view of the portable fluid warmer of FIG. 1illustrating the placement of the trigger within the reaction chamber;

FIG. 6 is a perspective view of the portable fluid warmer of FIG. 1illustrating an alternate placement of the trigger within the reactionchamber.

DETAILED DESCRIPTION OF THE INVENTION

Turning to the figures for a detailed explanation of the invention,there is illustrated a fluid heating device demonstrating by way ofexamples arrangements in which the principles of the present inventionmay be employed. FIG. 1 illustrates an embodiment of the device (10) ofthe present invention including a reaction chamber (11) for containingthe exothermic reaction. This reaction chamber further contains thetubing (12) in a planar serpentine arrangement through which theinfusion or transfusion fluid to be warmed can pass between inlet (14)and outlet (13). As illustrated in FIG. 2 the reaction chamber (11) hasa generally envelope shaped configuration. The reaction chambercomprises an upper sheet (11 a) and a lower sheet (11 b) there being aplurality of spaced apart connections, some of which are shown at (30)between the upper sheet and lower sheet.

The reaction chamber (11) is connected to a secondary chamber (15) thatcontains a reactive liquid compound needed for the exothermic reaction.Prior to use the reactive liquid in the secondary chamber (15) cannotenter the reaction chamber because the two chambers are separated by wayof a clamp (21), comprising a rigid plastic C section (17) and aflexible rubber insert (18), which acts as a barrier.

In use, the rigid plastic C-section (17) and flexible rubber insert (18)are removed, as illustrated in FIG. 3, allowing the reactive liquid toflow through an inlet port (16) into the reaction chamber (11). As thereactive liquid flows into the reaction chamber (11) it will come intocontact with the trigger that initiates the exothermic reaction. Toensure a more thorough exothermic reaction throughout the chamber (11)when the clamp (21) has been removed, the secondary chamber (15) can berolled, in the direction of arrow (22), around a pin (19), asillustrated in FIG. 4, pushing the reactive liquid along the length ofthe reaction chamber (11), as indicated by arrows 23. The upper sheet(11 a) and the lower sheet (11 b) of the reaction chamber are spacedapart approximately parallel to one another constrained by the pluralityof connections (30) when the reaction chamber is expanded by the ingressof reactive liquid.

The mechanical action of rolling the chamber improves the mixing of thereactive liquid with the trigger, allowing widespread crystallisation ofthe reactive liquid and hence faster release of heat to warm the liquidpassing through the tubing (12). When the reactive liquid has filled thereaction chamber, the reaction chamber can be rolled around thesecondary chamber, to form a compact bundle which can then be secured bya suitable means, such as an adhesive tape or hook and loop fastener(31, 32). The compact layout of the tubing (12) enables the averagedistance (24) for the reactive liquid to travel, from all points in thesecondary chamber (15) to all points in the reaction chamber (11) to berelatively small.

The trigger may be crystals (25) that are located adjacent inlet port(16), as illustrated in FIG. 5, such that as the reactive liquid movespast the crystals (25) in the direction of arrows 23 crystallisation isinitiated once the clamp (21) has been removed.

The rapid flow of the crystallising liquid chemical may be yet furtherenhanced by locating the trigger within the reaction chamber away fromboth the inlet port (16) to thereby create a liquid pathway or pathways(26) through the reaction chamber (11), as illustrated in FIG. 6.Keeping the inlet port (16) free of the trigger can reduce the tendencyfor crystals to grow and block or impede the movement of the liquidchemical into the chamber, while the provision of pathways (26) controlsthe crystallisation within the reaction chamber (11).

Accordingly, the above descriptions provide for the use of a fluidwarming device that employs relatively inexpensive materials andchemicals that provide for a temperature increase in order to warm theinfusion or transfusion fluids in a controlled manner. The low cost andthe simplicity of the apparatus make it very suitable for use inemergency situations or in situations where the unit may be stored for asubstantial amount of time without having to worry about problemsassociated with power supply. Since the fluid warming device islightweight, several may be carried in a field emergency medical kitoften used by rescuers travelling to remote locations.

Although the invention has been herein shown and described in what isconceived to be the most practical and preferred embodiment, however, itmust be understood that these particular arrangements merely illustrateand that the invention is not limited thereto. Accordingly the inventioncan include various modifications, which fall within the spirit andscope of the invention.

The invention claimed is:
 1. A warming device, for warming infusion ortransfusion fluids by an exothermic reaction of a reactive liquid,wherein said warming device comprises: a reaction chamber and asecondary chamber; the reaction chamber and the secondary chamber arealigned end on and are abutting; the reaction chamber containing atrigger; the reaction chamber being at least partially empty andunexpanded; the secondary chamber containing said reactive liquid; thesecondary chamber is compressible; an inlet port positioned between thesecondary chamber and the reaction chamber, the inlet port configured toallow passage of the reactive liquid from the secondary chamber into thereaction chamber to thereby expand the reaction chamber and contact ofthe reactive liquid with the trigger resulting in exothermic reactionand crystallization of the reactive liquid in the expanded reactionchamber; the inlet port being transversely elongate relative to the flowof the reactive liquid; the trigger being spaced apart from the inletport; a barrier closing the inlet port; tubing extending through thereaction chamber, the tubing extending from a tubing inlet to a tubingoutlet, the tubing defining a passageway between the tubing inlet andthe tubing outlet, the passageway configured to receive a flow of saidinfusion or transfusion fluids therethrough; and wherein the secondarychamber is configured to be rolled up, wherein the reaction chamber isconfigured to be rolled around the rolled up secondary chamber.
 2. Thewarming device of claim 1, wherein the reaction chamber is planar,comprising an upper sheet and a lower sheet, and comprising a pluralityof spaced apart connections there between.
 3. The warming device ofclaim 1, further comprises a compression member, being a rigid rodattached to the secondary chamber distal to the reaction chamber andtransverse to the direction of flow of the reactive liquid, wherein thesecondary chamber is configured to be compressed by rolling the rigidrod member over the secondary chamber.
 4. The warming device of claim 3,wherein the compression member is a rigid rod fastened at an end of thesecondary chamber opposite said inlet.
 5. The warming device of claim 1,wherein the reaction chamber comprises an upper sheet and a lower sheet,and wherein the trigger is attached to an inner surface of the uppersheet or the lower sheet or both.
 6. The warming device of claim 5,wherein the trigger is located throughout the reaction chamber.
 7. Thewarming device of claim 1, in a rolled up form; and a free end of therolled up reaction chamber secured to an adjacent portion of an outsideof the reaction chamber to retain the warming device in a rolled upform.
 8. The warming device of claim 1, wherein the barrier comprises atleast one of a frangible barrier or a removable barrier.
 9. The warmingdevice of claim 1, wherein the tubing, the reaction chamber, and thesecondary chamber are flexible.
 10. The warming device of claim 2,wherein the upper sheet and lower sheet are spaced apart parallel to oneanother and constrained by the plurality of spaced apart connectionswhen expanded.
 11. The warming device of claim 10, wherein at least oneof the upper sheet or the lower sheet are spaced apart from thepassageway when expanded.
 12. A warming device, for warming infusion ortransfusion fluids by an exothermic reaction of a reactive liquid,wherein said warming device comprises: a planar reaction chamber and asecondary chamber; the reaction chamber and the secondary chamber arealigned end on and are abutting; the reaction chamber containing atrigger; the reaction chamber comprising: an upper sheet; a lower sheetspaced apart and parallel to the upper sheet; and a plurality of spacedapart connections between the upper sheet and the lower sheet; thereaction chamber being at least partially empty and unexpanded; thesecondary chamber containing said reactive liquid; the secondary chamberis compressible; an inlet positioned between the secondary chamber andthe reaction chamber to allow passage of the reactive liquid from thesecondary chamber into the reaction chamber to thereby expand thereaction chamber and contact of the reactive liquid with the triggerresulting in exothermic reaction and crystallization of the reactiveliquid in the expanded reaction chamber; the inlet being transverselyelongate relative to the flow of the reactive liquid; the trigger beingspaced apart from the inlet; a frangible or removable barrier closingthe inlet; a passageway extending through said reaction chamber, thepassageway configured to receive a flow of said infusion or transfusionfluids therethrough; and the passageway, the reaction chamber and thesecondary chamber all being flexible, so that the secondary chamber canbe rolled up, wherein the reaction chamber can be rolled around therolled up secondary chamber, wherein the upper sheet and the lower sheetof the reaction chamber are configured to move apart, constrained by theplurality of spaced apart connections, upon ingress of the reactiveliquid into the expanded reaction chamber, and wherein at least one ofthe upper sheet or the lower sheet are spaced apart from the passagewayin the expanded reaction chamber.
 13. The warming device of claim 12,further comprising: a compression member, the compression membercomprising a rigid rod attached to the secondary chamber distal to thereaction chamber and transverse to the direction of flow of the reactiveliquid, wherein the secondary chamber is configured to be compressed byrolling the rigid rod member over the secondary chamber.
 14. The warmingdevice of claim 13, wherein the compression member comprises a rigid rodfastened at an end of the secondary chamber opposite said inlet.
 15. Anapparatus, comprising: a reaction chamber, the reaction chambercomprising a trigger, the reaction chamber being at least partiallyempty and unexpanded, the reaction chamber further comprising tubingextending through the reaction chamber from a tubing inlet to a tubingoutlet, the tubing defining a passageway between the tubing inlet andthe tubing outlet, the passageway configured to receive a flow of fluidtherethrough; a secondary chamber, the secondary chamber containing areactive liquid, wherein the secondary chamber is compressible; an inletport positioned between the secondary chamber and the reaction chamber,the inlet port comprising a barrier closing the inlet port, wherein saidbarrier is configured for opening, wherein upon barrier opening theinlet port is configured to allow a flow of the reactive liquid from thesecondary chamber into the reaction chamber to thereby expand thereaction chamber and contact of the reactive liquid with the triggerresulting in exothermic reaction and crystallization of the reactiveliquid in the expanded reaction chamber; the reaction chamber furthercomprising the trigger spaced apart from the inlet port; and thesecondary chamber configured to be rolled up and the reaction chamberconfigured to be rolled around the rolled up secondary chamber.
 16. Theapparatus of claim 15, wherein the tubing, the reaction chamber, and thesecondary chamber are flexible.
 17. The apparatus of claim 15, whereinthe barrier comprises at least one of a frangible barrier or a removablebarrier.
 18. The apparatus of claim 15, wherein the inlet port istransversely elongate relative to the flow of the reactive liquid. 19.The apparatus of claim 15, wherein the reaction chamber is planar,comprising an upper sheet and a lower sheet, and comprising a pluralityof spaced apart connections there between.
 20. The apparatus of claim19, wherein the upper sheet and lower sheet are spaced apart parallel toone another and constrained by the plurality of spaced apart connectionswhen expanded.